// Copyright 2018 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef V8_OBJECTS_JS_WEAK_REFS_H_
#define V8_OBJECTS_JS_WEAK_REFS_H_

#include "src/objects/js-objects.h"
#include "src/objects/microtask.h"

// Has to be the last include (doesn't have include guards):
#include "src/objects/object-macros.h"

namespace v8 {
namespace internal {

    class NativeContext;
    class WeakCell;

    // FinalizationGroup object from the JS Weak Refs spec proposal:
    // https://github.com/tc39/proposal-weakrefs
    class JSFinalizationGroup : public JSObject {
    public:
        DECL_PRINTER(JSFinalizationGroup)
        EXPORT_DECL_VERIFIER(JSFinalizationGroup)
        DECL_CAST(JSFinalizationGroup)

        DECL_ACCESSORS(native_context, NativeContext)
        DECL_ACCESSORS(cleanup, Object)

        DECL_ACCESSORS(active_cells, Object)
        DECL_ACCESSORS(cleared_cells, Object)
        DECL_ACCESSORS(key_map, Object)

        // For storing a list of JSFinalizationGroup objects in NativeContext.
        DECL_ACCESSORS(next, Object)

        DECL_INT_ACCESSORS(flags)

        inline static void Register(Handle<JSFinalizationGroup> finalization_group,
            Handle<JSReceiver> target,
            Handle<Object> holdings, Handle<Object> key,
            Isolate* isolate);
        inline static void Unregister(Handle<JSFinalizationGroup> finalization_group,
            Handle<Object> key, Isolate* isolate);

        // Returns true if the cleared_cells list is non-empty.
        inline bool NeedsCleanup() const;

        inline bool scheduled_for_cleanup() const;
        inline void set_scheduled_for_cleanup(bool scheduled_for_cleanup);

        // Remove the first cleared WeakCell from the cleared_cells
        // list (assumes there is one) and return its holdings.
        inline static Object PopClearedCellHoldings(
            Handle<JSFinalizationGroup> finalization_group, Isolate* isolate);

        // Constructs an iterator for the WeakCells in the cleared_cells list and
        // calls the user's cleanup function.
        static void Cleanup(Handle<JSFinalizationGroup> finalization_group,
            Isolate* isolate);

// Layout description.
#define JS_FINALIZATION_GROUP_FIELDS(V)  \
    V(kNativeContextOffset, kTaggedSize) \
    V(kCleanupOffset, kTaggedSize)       \
    V(kActiveCellsOffset, kTaggedSize)   \
    V(kClearedCellsOffset, kTaggedSize)  \
    V(kKeyMapOffset, kTaggedSize)        \
    V(kNextOffset, kTaggedSize)          \
    V(kFlagsOffset, kTaggedSize)         \
    /* Header size. */                   \
    V(kSize, 0)

        DEFINE_FIELD_OFFSET_CONSTANTS(JSObject::kHeaderSize,
            JS_FINALIZATION_GROUP_FIELDS)
#undef JS_FINALIZATION_GROUP_FIELDS

        // Bitfields in flags.
        class ScheduledForCleanupField : public BitField<bool, 0, 1> {
        };

        OBJECT_CONSTRUCTORS(JSFinalizationGroup, JSObject);
    };

    // Internal object for storing weak references in JSFinalizationGroup.
    class WeakCell : public HeapObject {
    public:
        DECL_PRINTER(WeakCell)
        EXPORT_DECL_VERIFIER(WeakCell)
        DECL_CAST(WeakCell)

        DECL_ACCESSORS(finalization_group, Object)
        DECL_ACCESSORS(target, HeapObject)
        DECL_ACCESSORS(holdings, Object)

        // For storing doubly linked lists of WeakCells in JSFinalizationGroup's
        // "active_cells" and "cleared_cells" lists.
        DECL_ACCESSORS(prev, Object)
        DECL_ACCESSORS(next, Object)

        // For storing doubly linked lists of WeakCells per key in
        // JSFinalizationGroup's key-based hashmap. WeakCell also needs to know its
        // key, so that we can remove the key from the key_map when we remove the last
        // WeakCell associated with it.
        DECL_ACCESSORS(key, Object)
        DECL_ACCESSORS(key_list_prev, Object)
        DECL_ACCESSORS(key_list_next, Object)

// Layout description.
#define WEAK_CELL_FIELDS(V)                  \
    V(kFinalizationGroupOffset, kTaggedSize) \
    V(kTargetOffset, kTaggedSize)            \
    V(kHoldingsOffset, kTaggedSize)          \
    V(kPrevOffset, kTaggedSize)              \
    V(kNextOffset, kTaggedSize)              \
    V(kKeyOffset, kTaggedSize)               \
    V(kKeyListPrevOffset, kTaggedSize)       \
    V(kKeyListNextOffset, kTaggedSize)       \
    /* Header size. */                       \
    V(kSize, 0)

        DEFINE_FIELD_OFFSET_CONSTANTS(HeapObject::kHeaderSize, WEAK_CELL_FIELDS)
#undef WEAK_CELL_FIELDS

        class BodyDescriptor;

        // Nullify is called during GC and it modifies the pointers in WeakCell and
        // JSFinalizationGroup. Thus we need to tell the GC about the modified slots
        // via the gc_notify_updated_slot function. The normal write barrier is not
        // enough, since it's disabled before GC.
        inline void Nullify(
            Isolate* isolate,
            std::function<void(HeapObject object, ObjectSlot slot, Object target)>
                gc_notify_updated_slot);

        inline void RemoveFromFinalizationGroupCells(Isolate* isolate);

        OBJECT_CONSTRUCTORS(WeakCell, HeapObject);
    };

    class JSWeakRef : public JSObject {
    public:
        DECL_PRINTER(JSWeakRef)
        EXPORT_DECL_VERIFIER(JSWeakRef)
        DECL_CAST(JSWeakRef)

        DECL_ACCESSORS(target, HeapObject)

// Layout description.
#define JS_WEAK_REF_FIELDS(V)     \
    V(kTargetOffset, kTaggedSize) \
    /* Header size. */            \
    V(kSize, 0)

        DEFINE_FIELD_OFFSET_CONSTANTS(JSObject::kHeaderSize, JS_WEAK_REF_FIELDS)
#undef JS_WEAK_REF_FIELDS

        class BodyDescriptor;

        OBJECT_CONSTRUCTORS(JSWeakRef, JSObject);
    };

    class FinalizationGroupCleanupJobTask : public Microtask {
    public:
        DECL_ACCESSORS(finalization_group, JSFinalizationGroup)

        DECL_CAST(FinalizationGroupCleanupJobTask)
        DECL_VERIFIER(FinalizationGroupCleanupJobTask)
        DECL_PRINTER(FinalizationGroupCleanupJobTask)

// Layout description.
#define FINALIZATION_GROUP_CLEANUP_JOB_TASK_FIELDS(V) \
    V(kFinalizationGroupOffset, kTaggedSize)          \
    /* Total size. */                                 \
    V(kSize, 0)

        DEFINE_FIELD_OFFSET_CONSTANTS(Microtask::kHeaderSize,
            FINALIZATION_GROUP_CLEANUP_JOB_TASK_FIELDS)
#undef FINALIZATION_GROUP_CLEANUP_JOB_TASK_FIELDS

        OBJECT_CONSTRUCTORS(FinalizationGroupCleanupJobTask, Microtask);
    };

    class JSFinalizationGroupCleanupIterator : public JSObject {
    public:
        DECL_PRINTER(JSFinalizationGroupCleanupIterator)
        DECL_VERIFIER(JSFinalizationGroupCleanupIterator)
        DECL_CAST(JSFinalizationGroupCleanupIterator)

        DECL_ACCESSORS(finalization_group, JSFinalizationGroup)

// Layout description.
#define JS_FINALIZATION_GROUP_CLEANUP_ITERATOR_FIELDS(V) \
    V(kFinalizationGroupOffset, kTaggedSize)             \
    /* Header size. */                                   \
    V(kSize, 0)

        DEFINE_FIELD_OFFSET_CONSTANTS(JSObject::kHeaderSize,
            JS_FINALIZATION_GROUP_CLEANUP_ITERATOR_FIELDS)
#undef JS_FINALIZATION_GROUP_CLEANUP_ITERATOR_FIELDS

        OBJECT_CONSTRUCTORS(JSFinalizationGroupCleanupIterator, JSObject);
    };

} // namespace internal
} // namespace v8

#include "src/objects/object-macros-undef.h"

#endif // V8_OBJECTS_JS_WEAK_REFS_H_
